The extent to which adopting energy-efficient technologies results in energy savings depends on how such technologies are used, and how monetary savings from energy efficiency are spent. Energy rebound occurs when potential energy savings are diminished due to post-adoption behaviour. It denotes that potential energy savings of adopting an energy-efficient technology or practice, possibly triggered by some policy, are offset by subsequent behavioural and systemic responses that increase energy use, resulting in diminished net energy savings.

Three main types of rebound are: direct rebound or intensity-of-use effect – a technology becomes more energy-efficient and thus less costly in its use, causing consumers or producers to use it more intensively; indirect rebound or re-spending effect – spending less due to using a more energy-efficient technology releases money that is subsequently spent on other products or services that use energy over their life cycle; and economy-wide rebound – more energy efficiency leads to many other changes in the economy, such as investments in expansion of production, impacts on capital and labour markets, and indirectly increases in consumption, all with consequences for energy use. The figure illustrates these rebound types, and their joint impact on energy savings, for the case of switching to a more fuel-efficient car.

We review empirical studies on how six behavioural regularities affect three energy-relevant decisions and ultimately rebound: adoption of energy-saving products or practices, their intensity of use and spending of associated monetary savings. The table with a summary of the findings indicates that behaviours that reflect limited rationality and willpower may increase rebound, while the effects of behaviours driven by bounded self-interest are less clear. We then describe how interventions associated with each of the behavioural regularities can influence rebound and thus serve to achieve higher energy savings. Future research ought to study energy-relevant decisions in a more integrated manner, with a particular focus on re-spending as this presents the greatest challenge for research and policy.

The capacity for language sets humans apart from all other animals. As long as scholars have been thinking about language there has been a debate as to why it evolved: is its core function to configure human-specific thought or is it rather mainly a tool for communication? The debates surrounding this question typically evolve around aspects of language that are used to express thoughts like "The dog is sleeping in my bed." However, there are other aspects of language which are dedicated to regulate communication and the expression of thought in conversational interaction is typically enriched in this way. Interactional aspects of language are used to regulate the construction of common ground as well as the interaction itself (e.g., turn-taking). Without interactional language (eh, yeah, right) the below conversation would sound curt, wheras its addition adds an interactive component that conveys that the speakers care about understanding each other.

I:  Gal Gadot was amazing as Wonderwoman, eh? R: Yeah, I know, right?

The fact that the language dedicated to interaction is as much part of language as the language dedicated for the expression of thought suggests that the function of language cannot be reduced to one or the other. And in fact, the same logic that configures the language of thought also configures the language of interaction. This logic, which we may refer to as a grammar of sorts, is arguably part of our genetic endowment, as evidenced by the fact that it is human-specific (animals communicate but they have no means to regulate their communication) and its acquisition is automatic (children automatically aquire interactional language just as they do the language they need to express the thoughts they want to communicate). In this way, the distinction between thought and communication dissolves: language unites them.